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Proceedings Paper

New concept of specification for mask flatness
Author(s): Masamitsu Itoh; Soichi Inoue; Katsuya Okumura; Tsuneyuki Hagiwara; Jiro Moriya
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Paper Abstract

The shrinkage of semiconductor devices creates demand for micronization in the photolithographic process. As a result, problems are arising in photolithography in the semiconductor manufacturing process. Focus latitude in photolithography becomes smaller as micronization advances and therefore the flatness of the mask can no longer be ignored. In this work, we clarified what the specification of mask flatness should be from the standpoint of its warpage in vacuum chucking of an exposure tool. A two-dimensional approach was applied for the prediction of mask surface after chucking. The approach is simple analytical calculation distinguishing between x-direction and y-direction. Warpage of mask surface after chucking has two modes depending on the directions. One is leverage caused by interaction of mask surface and chucking stage. Another one is warpage along chucking stage surface. The prediction shows good agreement with the actual surface of chucked mask. From this study, a new concept of the specification for mask blank flatness was proposed, taking warpage in vacuum chuck into consideration in the prediction. The proposed specification certainly can exclude masks that show large deformation after chucking even though with good free-standing flatness.

Paper Details

Date Published: 1 August 2002
PDF: 11 pages
Proc. SPIE 4754, Photomask and Next-Generation Lithography Mask Technology IX, (1 August 2002); doi: 10.1117/12.476957
Show Author Affiliations
Masamitsu Itoh, Toshiba Corp. (Japan)
Soichi Inoue, Toshiba Corp. (Japan)
Katsuya Okumura, Toshiba Corp. (Japan)
Tsuneyuki Hagiwara, Nikon Corp. (Japan)
Jiro Moriya, Shin-Etsu Chemical Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 4754:
Photomask and Next-Generation Lithography Mask Technology IX
Hiroichi Kawahira, Editor(s)

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